RAW mode avoids the usual lossy JPEG compression and save the images with the lossless TIFF format.
With regards to your capture settings and the results it might be more helpful to provide a screenshot of the settings you are using. With a setting of a 1 second interval between shots and 15 minutes total, you should get 15*60=900 shots which is neither what you got or what you expected.
TimeLapse will use stop & go with Galileo when it has enough time to perform the stop & go in time between shots. If you set the pan too aggressively (too big of an angle to move) for the time between shots, then it will fall back to using a continuous motion for the pan. What settings are you using for Galileo?